In this R34 research study we will develop and pilot-test a couples focused HIV prevention intervention addressing transgender women and their male primary partners. In the U.S., transgender women are among the highest-risk groups for HIV infection, and transgender women report most frequently engaging in unprotected sex with their male primary partners. Men who have sex with transgender women (MSTWs) have recently been identified as a high-risk population for HIV. Currently there are no evidence-based interventions to reduce HIV infection in transgender women or MSTWs. We propose an innovative research study that will adapt principles from empirically supported couples-focused HIV interventions in order to develop an intervention to reduce HIV risk in transgender women and their male primary partners. After adapting couples counseling materials, we will pilot test the couples-focused intervention with 60 couples comprising transgender women and their male primary partners. Findings will provide preliminary data on the effects, feasibility, acceptability, and implementation process of a couples HIV prevention intervention trial. If this research shows initial promise, we will use findings to support an R01 application to test intervention efficacy in a randomized controlled trial. PUBLIC HEALTH RELEVANCE: In this R34 Intervention Development study, we will adapt empirically supported couples HIV prevention interventions to address relationship dynamics between transgender women and their male primary partners. We will conduct a pilot test of the intervention to assess feasibility, acceptability, preliminary effect sizes, and trial implementation procedures. If findings show initial promise, this research will form the basis of a future randomized controlled trial of the first couples-focused intervention for transgender women and their male primary partners.